Zr/BaCrO4-based heat paper has been mainly utilized as a heat source for a thermal battery or as an ignition strip. A thermal battery is a kind of primary battery which is non-rechargeable. Since the electrolyte for a thermal battery is normally present in a solid phase having no ionic conductivity, it has no self-discharge and may thus be stored for a long period of time. A thermal battery is operated in such a manner that when an igniter or electric match is driven in response to an external signal as necessary, the generated flame may instantly combust a heat paper that is an ignition material, thus producing thermal energy, by which the heat, source is then ignited, and an electromotive force is generated while melting the solid electrolyte by the generated heat. However, when the combustion temperature of the heat paper is increased to a certain temperature or higher, the temperature of a battery stack in contact with the heat paper is increased to a temperature equal to or higher than a degradation temperature thereof, thus causing degradation of a cathode (FeS2), melting of an anode (LiSi) and localized overheating, undesirably deteriorating battery performance. In severe cases, thermal runaway of the battery may occur.